Hydraulic and/or pneumatic door closers for controlling closing characteristics of swing doors are well known and have been in wide use (see, for example, U.S. Pat. Nos. 4,793,023, 4,414,703 and 4,378,612). Primarily hydraulically or pneumatically operated openers and/or opening assist mechanisms are also known (see U.S. Pat. Nos. 3,948,000, 3,936,977, 4,995,194 and 4,429,490). Similarly, a variety of electromechanical automatic door operators have been heretofore known and/or utilized (see U.S. Pat. Nos. 2,910,290, 3,127,160, 4,045,914 and 4,220,051). Each (hydraulic and/or pneumatic and electromechanical operators) has its own unique advantages and disadvantages.
There has also been some attempt at combining these approaches so that at least some of the advantages of each are utilized (see, for example, U.S. Pat. Nos. 3,874,117, 3,129,936, 1,684,704, 2,256,613, and 4,438,835). Such approaches to door controllers have for the most part sought to utilize the hydraulic mechanism merely as a speed control (i.e., not as an independently functioning unit), and/or have utilized each type of operator in parallel connection with the door rather than in conjunction. Such approaches are not entirely satisfactory due to lack of attractiveness arid additional space requirements adjacent to the door, expense of manufacture and/or operation (for example, where a clutch or other disengagement mechanism is required for operation, or where a motor is in constant operation for causing both opening and active door closing, and/or undue control complexity required to achieve reliability and to meet door operating standards.
In view of recent concern and legislation regarding provision of access for the disabled to various public and private buildings, it would be desirable to provide a low cost, low power and reliable apparatus for use with a standard, typically hydraulically dampening, door closer arrangement to provide a door operator which meets the accessibility requirements of the disabled while preserving the functionality and meeting compliance requirements of the standard door closer.
Typical compliance requirements, such as those established in the A.N.S.I. guidelines, include minimum efficiency standards for door closers. In U.S. Pat. No. 4,995,194, wherein a hydraulic pump is utilized to move fluid, and thus a piston, to assist with door opening, door closing efficiency is maintained by using the same hydraulic flow path or paths for closing as has been traditionally used by such door closers. In this manner (utilizing no additional components directly connected to the existing piston) no additional drag is placed on the system and thus the efficiency is unchanged. In order to meet efficiency requirements while using an electromechanical drive to open the door, either carefully controlled motor driven opening and closing or various clutching mechanisms for decoupling an electromechanical drive during the closing cycle (particularly necessary in the event of an interruption of power supply) have generally been required.
Improvement of door operators directed to maintaining and/or enhancing the utility and efficiency of traditionally utilized hydraulic or pneumatic door closers, while selectively providing low power yet fully automatic door opening and/or opening assistance, without undue complication and expense, could thus be utilized.